1. Field of the Invention
The present invention relates to an optical sensor and an image forming apparatus, and in particular, to an optical sensor suitable for identifying an object, and an information processing apparatus including the optical sensor.
2. Description of the Related Art
An image forming apparatus such as a digital copier, a laser printer or the like transfers a toner image onto a surface of a recording medium typified by printing paper, fixes the toner image by heating and pressing it under predetermined conditions and thus forms an image. What is to take into consideration are conditions of a heating amount and/or a pressure during the fixing process, and in particular, in order to carry out image forming of high quality, it is necessary to set fixing conditions separately for each recording medium.
This is because image quality on a recording medium greatly depends on the material, thickness, humidity, smoothness, coated state and so forth. For example, concerning smoothness, a fixing rate may be degraded at dented parts of an uneven surface of printing paper depending on fixing conditions. Then, color heterogeneity may occur unless fixing is carried out under proper conditions suitable for a recording medium.
As recently image forming apparatuses have been advancing and expression methods have been diversifying, there are hundreds or more of types of recording media only for printing paper, and further, for each one of respective types, there are a wide variety of brands depending on specifications such as weights, thicknesses and so forth. For forming an image of high quality, it is necessary to finely set fixing conditions for each one of these brands.
Further, recently, the number of the brands has been increasing also for plain paper, coated paper typified by gloss coated paper, matt coated paper and art coated paper, plastic sheets and special paper with emboss effect on the surface thereof.
In a current image forming apparatus, a user himself or herself should set fixing conditions. Thus, there is troublesomeness such that the user is required to have knowledge for identifying the type of paper, and also, the user himself or herself should input setting contents according to the type of paper each time. Then, if the user makes a mistake concerning the setting contents, the user cannot obtain an optimum image.
Patent Reference No. 1 (Japanese Laid-Open Patent Application No. 2002-340518) discloses a surface nature identification apparatus including a sensor for identifying the surface nature of a recording material surface by coming into contact and scanning it.
Patent Reference No. 2 (Japanese Laid-Open Patent Application No. 2003-292170) discloses a printing apparatus identifying the type of paper using a pressure value detected from a pressure sensor coming into contact with the paper.
Patent Reference No. 3 (Japanese Laid-Open Patent Application No. 2005-156380) discloses a recording material identification apparatus identifying the type of a recording material using reflected light and transmitted light.
Patent Reference No. 4 (Japanese Laid-Open Patent Application No. 10-160687) discloses a sheet material identification apparatus identifying the material of a moving sheet material based on a reflected light amount reflected from a surface of the sheet material and a transmitted light amount transmitted by the sheet material.
Patent Reference No. 5 (Japanese Laid-Open Patent Application No. 2006-062842) discloses an image forming apparatus having a determination part that determines whether there is recording material contained in a paper supply part and whether there is the paper supply part, based on a detection output from a reflective optical sensor.
Patent Reference No. 6 (Japanese Laid-Open Patent Application No. 11-249353) discloses an image forming apparatus determining the surface nature of a recording medium upon emitting light to the recording medium and detecting respective light amounts of two polarization components of reflected light from the recording medium.
However, it may be difficult to identify an object in detail without much increasing the apparatus cost and/or size.